The plane wreck Mikael encounters is a real wreck. In 1973 a United States Navy Douglas C-117D plane ran out of fuel and crashed on the black beach at Sólheimasandur, in the South Coast of Iceland. Fortunately, everyone in that plane survived. Later it turned out that the pilot had simply switched over to the wrong fuel tank. The remains are still on the sand very close to the sea.
Filming for Katla began in early 2020 but was suspended after the Covid-19 virus reached Scandinavia. Filming resumed in May of 2020 at a large studio in Reykjavik for interior scenes and eventually on location in the real village of Vik, which is normally a heavily-visited tourist locale but was empty during pandemic travel restrictions for much of 2020. Pre-pandemic Vik also had a revolving resident population of geologists and volcanologists numbering in the hundreds, absent during filming. Series co-creator and director Baltasar Kormakur commented that returning to a deserted Vik to shoot exteriors "was like 28 Days Later".
The amphibious cargo ferry used in the film is a Mil-Spec LARC-XV (Lighter, Amphibious Resupply, Cargo, 15-ton), manufactured briefly in the 1960s by the military division of the Fruehauf Trailer Corp in the USA. Similar commercial amphibious ferries are used in southern Iceland for coastal sightseeing expeditions but the filmmakers are likely inferring that the year-old fictional eruption in the film has cut off Vik from road access because of ash deposits, lahars, or glacial melt flooding. Resupply or airlift services by helicopter in an airspace contaminated by ejecting volcanic ash would be extremely hazardous as well as prohibitively expensive.
In February 2017, Variety magazine reported that Baltasar Kormákur would be working on Katla, a supernatural drama series centered on the volcano of the same name, with filming to take place outside Reykjavík.